The advantageous configurations and operation of current-mode logic is well known. A multiple input current-mode logic NOR gate exhibits a propagation delay which is longer, and a stronger function of temperature than the propagation delay for a multiple input current-mode logic OR gate. One reason is that the maximum forward bias across the base-collector junction of the output transistor is one-half of a logic voltage swing for the OR gate, but a full logic voltage swing for the NOR gate. A second reason is that the capacitance at the output node is lower for the OR gate because the collector of only one transistor is connected to the output node and all the collectors for the input transistors are connected directly to the most positive supply voltage. For a given logic function implementation, the number of noninverting OR gates could be maximized without increasing the number of stages of delay if a compatible noninverting AND gate was available. Accordingly, an object of this invention is a noninverting current-mode logic AND gate which is compatible with other current-mode logic configurations.
It is a further object of the invention also to provide current-mode logic circuits of the OR/AND configuration having enhanced speed and greater packing density than heretofore realized in such logic arrangements.